Bicycle, in particular an all-terrain bicycle

ABSTRACT

A bicycle, in particular an all-terrain bicycle, with a front wheel which can be pivoted by means of a handlebar, a rear wheel, and a rear wheel drive assembly comprising a pedal unit, a transmission (19), and a gear element. The front wheel is driven by way a transmission interconnecting the rear wheel a cardan joint and another transmission interconnecting the cardan joint and the front wheel.

The invention relates to a bicycle, in particular an all-terrainbicycle, comprising frame, a front wheel, a rear wheel, a handle bar forsteering the front wheel, a pedal unit, the front wheel, the rear wheel,the handle bar and the pedal unit being rotatably mounted on the frame,a transmission connecting the pedal unit to the rear wheel fortransmitting a drive thereto, transmission means connecting the rearwheel to the front wheel for transmitting the drive to the front wheel.

Various bicycles are already known, in which in addition to the driveassembly for the rear wheel, a drive assembly is provided for the frontwheel. A known all-wheel drive for the two wheels of a bicycle accordingto DE-OS 33 19 105 is provided with a multiple stage variable gear forthe conversion of a driving Force, applied via a pedal lever or a motorwith a reciprocating or revolving movement onto the wheel hub shafts ofthe wheels.

Furthermore, a force transmission--according to the DE-OS 38 31 890--isknown, in which the rear wheel and if necessary the front wheel can bedriven via a continuously adjustable force transmission throughutilization of an oscillating swivel movement of a pedal lever.

Finally, drive arrangements with separate crank gears for the rear wheeland the front wheel of a bicycle are known, in which one crank gear isoperated by the legs and the other by the hands. These known all-wheeldrives are very costly, because they require many drive elements or gearelements for the transmission of the driving force onto the wheels.

It is an object of the present invention to create a bicycle, inparticular an all-terrain bicycle, in which the rear wheel and the frontwheel can be selectively driven together, and in which the drivearrangements require only a small number of drive elements.

This object of the invention is solved in a bicycle of thefirst-indicated type with a cardan joint comprising a driving shaftmounted on the frame for rotation about a central axis and a drivenshaft mounted on the handle bar for rotation about a central axis, thedriving shaft and driven shaft being universally movable in relation toeach other from a position wherein the central axes thereof are inalignment with each other and the central axes extending parallel to thehandlebar when in alignment. The transmission means comprises atransmission connecting the pedal unit to the rear wheel fortransmitting a drive thereto, a transmission connecting the rear wheelto the driving shaft for transmitting the drive of the rear wheel to thedriving shaft whereby a drive is imparted to the driving shaft, and atransmission connecting the driven shaft to the front wheel fortransmitting the drive of the driving and driven shafts to the frontwheel. The surprising advantage of this drive arrangement, connectingthe drive elements of the rear wheel and of the front wheel, lies in thesimultaneous drive of the front wheel in direct dependence on therotational behaviour of the rear wheel, in which, independently of anytranslation changes through a switching device in the drive arrangementfor the rear wheel, the force transmission takes place simultaneouslyonto the front wheel, in which through a high degree of efficiency agood utilization of the driving energy is achieved.

According to one feature of this invention, the handlebar is rotatableabout a swivel axis and the driving shaft and driven shaft extend atrespective sides of the swivel axis, the aligned central axes thereofextending perpendicularly to the swivel axis and the swivel axisintersecting the central axes at a common point of intersection. Thiseffectively avoids impairment of the swivel movement of the front wheelon steering.

A further embodiment, wherein the transmissions connecting the rearwheel to the driving shaft and the driven shaft to the front wheelcomprise roller chains, further comprises sprockets engaged by theroller chains and respectively affixed to the driving and driven shaftsfor rotation therewith. This is advantageous because thereby driveelements which have already proved successful in operation can be usedfor the drive of the front wheel, whereby cost-intensive specialcomponents are eliminated, and thereby the all-wheel drive can beproduced economically. It is also advantageous to provide additionalsprockets respectively affixed to the front and rear wheels, theadditional sprockets being engaged by the roller chains, because therebyhigh moments of rotation, as occur in particular on all-terrainjourneys, can be transferred without hindrance.

Another embodiment comprises a detachable coupling arrangement affixingthe additional sprocket to the rear wheel hub, whereby the drivearrangement for the front wheel can be selectively disconnected, inorder, for example, when using the bicycle on flat terrain orrespectively on a secure base, to reduce the frictional losses which arehigher with a greater number of drive elements.

If the front and/or rear wheel comprises a hub, a freewheelingarrangement may affix each of the additional sprockets respectively tothe front and rear wheel, whereby the drive elements are coupled withthe drive axes only when a propulsive output occurs and the drivearrangement is not also moved, e.g. when riding downhill.

It is also advantageous if a casing covers the transmission connectingthe driving shaft to the rear wheel, whereby the rider of the bicyclecan be protected from the moving drive means.

If the casing includes a guide element for the transmission, the guideelement consisting of an abrasion-resistant material having a lowfriction coefficient, a guidance is achieved for the transmission means,which is free of wear and has minimal driving losses.

It is also advantageous if the bicycle further comprises attachmentmeans for affixing the casing to the frame, whereby the mounting of thedrive arrangement does not require any additional attachment elementsand can be carried out very simply without special tools.

According to a further advantageous embodiment, the transmissionsrespectively connecting the front and rear wheels to the driven anddriving shafts extend in parallel planes spaced a small distance apartfrom each other, whereby a very compact structural unit is achieved forthe drive arrangement of the front wheel.

For a better understanding of the invention, the latter is explained infurther detail with the aid of the embodiments illustrated in thedrawings, in which:

FIG. 1 shows a bicycle according to the invention, with an additionaldrive arrangement for the front wheel, in side view;

FIG. 2 shows a transmission device, according to the invention, of thedrive device according to FIG. 1, in schematic, diagrammaticrepresentation;

FIG. 3 shows the drive device, according to the invention, for the frontwheel with the transmission device according to FIG. 2 in side view;

FIG. 4 shows the drive device according to the invention in front viewin section, according to lines IV--IV in FIG. 3;

FIG. 5 shows another variant embodiment of a bicycle with an all-wheeldrive arrangement according to the invention, in plan view;

FIG. 6 shows the bicycle according to FIG. 5 in side view;

FIG. 7 shows a reversing gear for a drive arrangement according to theinvention, in side view;

FIG. 8 shows a front view of a further embodiment of a drive arrangementaccording to the invention;

FIG. 9 shows a drive scheme for a bicycle according to the invention,with a drive arrangement for the rear-and the front wheel;

FIG. 10 shows another variant of the drive arrangement;

FIG. 11 shows detail view of another embodiment of the drive arrangementin simplified, schematic representation;

FIG. 12 shows a guide arrangement according to the invention for thedrive arrangement, partially in section;

FIG. 13 shows another embodiment of the drive arrangement according tothe invention in schematic representation.

FIGS. 1 to 4 show bicycle 1 comprising frame 2, in particular of tubularframe parts 3,4, which are welded or soldered to each other atintersections. In mountings of the fork-shaped frame part 4, a rearwheel 5 is rotatably mounted about an axis 8 running horizontally to astanding surface 6 and perpendicularly in relation to a direction oftravel--arrow 7.

In a mounting 9 of a fork-shaped frame part 10 a front wheel 11 isrotatably mounted about an axis 12 arranged parallel to the axis 8. Thefork-shaped frame part 10 has in the direction opposed to the standingsurface 6 a cylindrical extension 13, which is rotatably mounted in atubular frame part 14, arranged approximately vertically, for rotatingabout a swivel axis 15. To carry out a swivel movement about the swivelaxis 15, the extension 13 has a handlebar 16, which is fastened on theextension 13 approximately parallel to the standing surface 6.

The bicycle 1 has a known drive arrangement 17 for the rear wheel 5,which is formed by a pedal unit 18, Transmission 19 and drive elements20. The Transmission 19 is formed in a preferred manner by a rollerchain 21. The pedal unit 18 and the drive element 20 have sprocketsengaging the roller chain. In addition, the drive arrangement 17comprises a switch device to alter the ratio between the pedal unit 18and the rear wheel 5. Such a switch arrangement, in which atranslation-speed change is brought about by placing the roller chain 21between different pairs of toothed wheels between the pedal unit 18 andthe drive elements 20 of the rear wheel 5, is known for example asShimao-switching type NEW, as used in bicycles, in particular mountainbikes of the firm KTM. A drive arrangement 22 is arranged between therear wheel 5 and the front wheel 11, for the transmission of arotational moment component of the rotational moment imparted to therear wheel 5 via the drive arrangement 17. This comprises a driveelement 23, which is affixed to the drive element 20 so as to rotatetherewith, a transmission 24, e.g. a roller chain 21 and a transmissiondevice 25, in particular in the region of the handlebar 16, whichfurther transmits the rotational moment to the front wheel 11 via an--inparticular endless--transmission 26, e.g. a roller chain 21 engaging adrive element 27 of the front wheel 11.

In FIGS. 2 to 4, the transmission device 25 and its arrangement in theregion of the handlebar 16 and the swivel axis 15 is shown in greaterdetail. The transmission device 25 is formed by a coupling element 29,having a cardan joint 28, and coupling parts 30,31 rotatably mounted onbearing elements 32,33. On the coupling parts 30,31 there are arrangeddrive elements 34,35, affixed to the latter so as to rotate therewith,such as sprockets for the endless roller chains 21. Central axes 36,37of the coupling parts 30,31 form a common point of intersection 38 withthe swivel axis 15, the central axes 36,37 being arranged approximatelyat right angles to the swivel axis 15. The bearing element 33, bearingthe coupling part 31, is attached via a spacer tongue 39 on thehandlebar 16, whilst the further bearing element 32 is attached via aspacer tongue 40 to the frame part 3 of the frame 2. Through thearrangement of the cardan joint 28 between the coupling parts 30,31 andits position in relation to the swivel axis 15, the rotational momentcan be transferred independently of a swivel movement according to acircular double arrow 41. Instead of the cardan joint 28 which is shown,multiple universally articulated coupling elements 29 may be used, inorder to make possible even greater swivel movements of the front wheel11 about the swivel axis 15. Of course, the transmission means 24,26 andthe transmission device 25 can be arranged with the drive elements 34,35inside casing elements 42, as illustrated FIG. 1, in particular of lightplastics components.

The connection of the drive element 23 with a rear wheel hub 43 so as tobe secure with respect t o rotation may take place via a knownfreewheeling arrangement 44 or a disconnectable coupling arrangement 45,whereby the drive arrangement 22 can be disconnected or connected asrequired. Of course, it is also possible to arrange the freewheelingarrangement 44 and/or the coupling arrangement 45 between the driveelement 27 and a front wheel hub 46 of the front wheel 11.

In FIGS. 5 and 6, the bicycle 1 is shown with another variant of thedrive arrangement 22. In this variant, a flexible shaft 47 is arrangedas transmission means between the rear wheel hub 43 and the front wheelhub 46 . The flexible shaft 47 has a fixed casing 48, in which an innercore 49 is rotatably mounted, which is formed in particular from a wirecable. The end regions of the casing 48 are attached to the frame parts4,10 associated with the rear wheel 5 and the front wheel 11, in which alongitudinal central axis 50 of the shaft 47 forms approximately a rightangle to the axes 8,12 of the rear wheel 5 and of the front wheel 11.The force-locking drive connection between the rear wheel 5 and thefront wheel 11 with the inner core 49 is achieved by means of bevel geararrangements 51,52 within each case a pinion 53 at the ends of theflexible shaft 47 and a drive wheel 54 on the rear wheel hub 43 and adrive wheel 55 on the front wheel hub 46. Thereby, the drivingrotational moment applied via the pedal unit 18 and the drivearrangement 17 is distributed equally onto the rear wheel 5 and thefront wheel 11. To achieve the same direction of rotation of the rearwheel 5 and of the front wheel 11, the bevel gear arrangements 51,52 arearranged on different sides of the rear or front wheel hub 43,46, inrelation to the direction of travel--arrow 7. A special outline of theflexible shaft 47 to avoid small deflection radii 56 is shown along theframe parts 3,10,14. Thereby, it is also possible to attach the flexibleshaft 47 by means of holding elements 57, e.g. clamps, on the frameparts 3,10,14, just as it is also possible to guide the flexible shaft47 in partial regions inside the tubular frame parts 3,10.

The arrangement of a preferably switchable reversing gear 58, throughwhich graduated rotational moments can be applied onto the rear or frontwheel 5,11, is shown in dot-and-dash lines. This reversing gear 58divides the flexible shaft 47 into two lines in each case between therear wheel hub 43 and the reversing gear 58 and the latter and the frontwheel hub 46. At the same time, the reversing gear 58 brings about areversal of the direction of rotation between the two lines of theflexible shaft 47, whereby with the application of the reversing gear 58the bevel gear arrangements 51,52 can be arranged on the same side ofthe rear wheel hub or front wheel hub 43,46.

In FIG. 7 the reversing gear 58 is shown. In an approximately squarehousing 59, which is attached to the frame part 3 e.g. with a pipe clip,stub shafts 60,61 of two lines of the flexible shaft 47, runningparallel to each other, are arranged so as to be rotatably mounted. Onthe stub shafts 61 a double toothed wheel 62, in one piece, is mountedso as to be secure with respect to rotation via a switching lever 66,engaging in a forked shape into an annular groove 63 between the toothedrings 64,65 of the double toothed wheel 62, so as to be longitudinallydisplaceable in longitudinal direction of the stub shaft 61. On the stubshaft 60 running in parallel, toothed rings 67,68 are arranged at adistance 69 from each other, which is greater than a distance 70 betweenthe toothed wheels 64,65 plus a width 71 of the toothed ring 65, wherebyon a longitudinal displacement of the double toothed wheel 62 in eachcase a toothed ring 64,65 can cooperate with a toothed ring 67,68. Thetoothed rings 67,68 are movable rotatably relative to each other via afriction coupling 72, in which one of the toothed rings 67,68 isconnected with the stub shaft 60 so as to be secure with respect torotation.

Through graduation from the nominal diameter 73 of the toothed rings64,65,67,68, in a known manner an at least two-stage translation changecan be undertaken in a fixed ratio, in which it is expedient to arrangeat least one translation ratio through selection of the same nominaldiameter 73 of the toothed rings 64,67 or 65,68, to be brought intoengagement, for the translation ratio 1:1. Thereby also the drivingrotational moment is also effective in equal parts on the rear wheel 5and the front wheel 11. A translation ratio deviating therefrom is thenexpedient, when the driving rotational moment is to be distributedunequally, e.g. when riding inclines where the load on the rear wheel isgreater, and therefore a higher driving moment can become effective. Theequalization of the rotation rates between the rear wheel 5 and thefront wheel 11 takes place in this case through the relative mobility ofthe toothed rings 67,68 with respect to each other, which is possiblevia the friction coupling 72.

A ratio deviating from the translation ratio 1:1, which can be set in achangeable manner, is advantageous in particular when owing toparticular conditions of use wheels of different size come to be used onthe bicycle 1. Thus, in different disciplines of cycling sport it isusual to use a front wheel 11, which has a smaller diameter than therear wheel 5. In such a case, in the reversing gear 58 in the selectionof the corresponding translation ratios, the different rotation rate ofthe rear wheel 5 and the front wheel 11 is balanced out.

For a reliable operation of a bicycle on an uneven terrain and onunpaved paths, through an additional drive of the front wheel acorrespondingly higher operating reliability is achieved. Devices suchas, e.g. freewheeling devices here can interrupt a driving line, e.g. tothe front wheel, dependent on use, such that the transmission means areput at a standstill, when no propulsive force is to be applied, such as,for example, on riding over inclines. Instead of the reversing gear 58,operating on a mechanical principle, the friction coupling 72, of coursea rotation moment converter, based on the hydraulic principle, can alsobe used for the continuous selection of a translation ratio, and alsothe arrangement of a so-called viscose coupling to determine therotation rate with a different translation ratio for the rear wheel orthe front wheel. In FIG. 8 a further embodiment of a drive arrangementis shown for the front wheel 11 of a bicycle 1. The fork-shaped framepart 10, supporting the front wheel 11, has a C-shaped transition part74 in the direction of the extension 13, mounted in the frame part 14 soas to be orientable about the swivel axis 15. Parallel to the axis 12 ofthe front wheel 11, in a lug 75 of the C-shaped transition part 74, thebearing element 33 for the coupling part 31 of the cardan joint 28 isarranged. The drive element 35 is attached on a stub shaft 76 of thecoupling part 31. On the fixed frame part 14, via the spacer tongue 40,the further bearing element 32 for the coupling part 30 and the driveelement 34 attached thereon, are arranged. In the unswivelled positionof the front wheel 11 about the swivel axis 15 and in relation to alongitudinal axis of the bicycle 1, the central axes 36,37 of thecoupling parts 30,31 are arranged in alignment with each other. In afree space 77 formed by the C-shaped transition part 74, the cardanjoint 28 connecting the coupling parts 30,31 is arranged, in the midpoint of which the swivel axis 15 and the central axes 36,37 intersect.Thereby, the transmission takes place of the driving rotational momentvia the drive element 34, attached non-orientably to the frame part 14,and via the cardan joint 28, to the drive element 35, which isorientable about the swivel axis 15, and via the transmission 26, e.g.the roller chain 21, to the drive element 27 of the front wheel 11. Thearrangement of the cardan joint 28 therefore makes possible thetransmission of the driving rotational moment between the two driveelements 34,35 which are orientable relative to each other.

In FIG. 9 a drive scheme for the drive arrangement of the bicycle 1 isshown, with the drive arrangement 22 for the front wheel 11, in which,to clearly show the drive elements the frame parts of the bicycle 1 wereomitted. The drive arrangement 17 for the rear wheel 5 comprises thepedal unit 18, the transmission means 19, the drive elements 20 and aswitching arrangement 78 in the region of the pedal unit 18, to placethe transmission means 19 onto chain wheels 79 having differentdiameters. A further switching arrangement 80 is arranged to place thetransmission means 19 on chain wheels 81, having different diameters,for the rear wheel 5. Via the coupling device 45, e.g. a switchable clawcoupling 82, friction coupling or the like, the conical output wheel 54of the bevel gear arrangement 51 is able to be brought in and out ofengagement with the rear wheel hub 43. Between the bevel geararrangement 51 and the further bevel gear arrangement 52, cooperatingwith the front wheel hub 47 so as to be secure with respect to moment ofrotation, the flexible shaft 47 is arranged on the bicycle 1 so as to besecure with respect to rotation, with the covering 48, and supports,movable rotatably, the inner core 49 with the pinions 53, which areconnected with the inner core 49 so as to be secure with respect torotation. In order to make possible, for example, a riding downhillwithout blocking the drive arrangement 22 or the flexible shaft 47 inthe rolling state of the bicycle 1, i.e. without the application of adriving rotational moment, there are arranged between the drive element20 and the rear wheel hub 43 and the bevel gear arrangement 51 and thefront wheel hub 46 known free wheeling arrangements 44, such as, forexample, roller elements 83 or the like, transferring rotational forceonly in one direction.

In FIG. 10 a drive scheme is shown for the drive arrangement of thebicycle 1 with the drive arrangement 17 for the rear wheel 5 and thedrive arrangement 22 for the front wheel 11. Here, the pedal unit 18 andthe reversing gear 58 form a drive arrangement 84 in which a switchingarrangement 85 is arranged for different translation ratios between adrive axis 87, conected with pedal units 86, and a drive shaft 88. Theswitching arrangement 85 is based here on the principle of the known hubinner switching. From the drive arrangement 84, the driving rotationalmoment, applied via the pedal unit 18, is passed via the drivearrangement 17 to the drive element 20 of the rear wheel 5 and the drivearrangement 22 to the drive element 27 of the front wheel 11, in whichthe transmission means 19,26 may be formed by roller chains 21 orflexible shafts 47, in which preferably the transmission means 26associated with the front wheel 11 is formed by the flexible shaft 47.

In FIGS. 11 and 12 a further embodiment of the drive arrangement 22 isshown. In this arrangement, a guide arrangement 89, consisting of anI-section 90, is attached to the frame part 3 of the bicycle 1 viaattachment elements 91, e.g. pipe clamps 92. In recesses 93 of theI-section 90, the transmission 24, e.g. a roller chain 21, is guided.The I-section 90 consists for example of an abrasion-resistant materialsuch as metal, plastics, fibre-reinforced plastics etc., which at thesame time has a low friction coefficient, whereby a high wear-resistanceis produced, and also low frictional losses occur. The recesses 93,acting as longitudinal guide for the transmission 24 are covered forexample by U-sections 94, which are detachably secured to cross-pieces95 of the I-section 90, e.g. are screwed thereto, whereby these form aneffective contact protection for the rider of the bicycle 1.

The drive arrangement 17 for the rear wheel 5 with the transmission 19,e.g. the roller chain 21 and the drive arrangement 22 with thetransmission 24 are arranged in parallel planes spaced apart a distance96 which corresponds approximately to a width 97 of the drive element 20or 23. It is expedient here if the drive arrangement 22 has a greaterdistance 98 from the rear wheel 5 than the drive arrangement 17, wherebya subsequent equipping of the bicycle 1 with the drive arrangement 22 isfacilitated. It is additionally advantageous if the drive element 23 ismounted via a freewheeling arrangement 99 on the axis 8 of the rearwheel 5. This freewheeling arrangement 99, known per se, ensures thetransmission of a drive moment only in a rotational direction of thedrive element 23 and enables the drive arrangement 22 to be stopped whenriding downhill, i.e. that in such an operating state this, and hencethe transmission 24, is at a standstill, whereby transmission lossesthrough friction and increased wear are avoided.

In FIG. 13, a drive scheme is shown of a further embodiment of the drivearrangement 22 for the front wheel 11. Via the drive arrangement 17, theforce applied onto the pedal unit 18 is transferred to the rear wheel 5.On the side of the rear wheel 5, opposed to the drive arrangement 17,the drive arrangement 22 for the front wheel 11 is arranged, and via theclaw coupling 82 is able to be coupled in a force-locking manner withthe rear wheel 5. The transmission 24 of the drive arrangement 22 formshere the force transmission to the cardan joint 28, which is arranged inthe region of the handle bar 16. Via the cardan joint 28, the flux offorce then takes place onto the side of the front wheel 11, opposed tothe drive arrangement 22, and via the transmission 26 onto the frontwheel 11. Through the arrangement of the claw coupling 82, the drivearrangement 22 can now be switched on or off selectively by the riderfor the force-locking connection between the rear wheel 5 and the frontwheel 11. Of course it is also, moreover, possible to equip the driveelement 27, which is connected so as to be rotationally movable with thefront wheel 11, with a known freewheeling arrangement 44.

For a better understanding of the invention, individual parts wereillustrated distorted on an unproportional scale In addition, individualcombinations of features described as a whole in the illustratedembodiments may form independent solutions in accordance with theinvention.

LIST OF REFERENCE NUMBERS

1 bicycle

2 frame

3 frame part

4 frame part

5 rear wheel

6 standing surface

7 arrow

8 axis

9 mounting

10 frame part

11 front wheel

12 axis

13 extension

14 frame part

15 swivel axis

16 handlebar

17 drive arrangement

18 pedal unit

19 transmission means

20 drive element

21 roller chain

22 drive arrangement

23 drive element

24 transmission means

25 transmission device

26 transmission means

27 drive element

28 cardan joint

29 coupling element

30 coupling part

31 coupling part

32 bearing element

33 bearing element

34 drive element

35 drive element

36 central axis

37 central axis

38 point of intersection

39 spacer tongue

40 spacer tongue

41 double arrow

42 covering element

43 rear wheel hub

44 freewheeling arrangement

45 coupling arrangement

46 front wheel hub

47 shaft

48 casing

49 inner core

50 longitudinal central axis

51 bevel gear arrangement

52 bevel gear arrangement

53 pinion

54 drive wheel

55 drive wheel

56 deflection radius

57 holding element

58 reversing gear

59 housing

60 stub shaft

61 stub shaft

62 double toothed wheel

63 groove

64 toothed ring

65 toothed ring

66 switching lever

67 toothed ring

68 toothed ring

69 distance

70 distance

71 width

72 friction coupling

73 nominal diameter

74 transition region

75 projection

76 stub shaft

77 free space

78 switching arrangement

79 chain wheel

80 switching arrangement

81 chain wheel

82 claw coupling

83 roller element

84 drive arrangement

85 switching arrangement

86 pedal unit

87 drive axis

88 drive shaft

I claim:
 1. A bicycle comprising(a) a frame, (b) a front wheel, (c) a rear wheel, (d) a handle bar for steering the front wheel, (e) a pedal unit,(1) the front wheel, the rear wheel, the handle bar and the pedal unit being rotatably mounted on the frame, (f) a cardan joint comprising(1) a driving shaft mounted on the frame for rotation about a central axis and (2) a driven shaft mounted on the handle bar for rotation about a central axis, (3) the driving shaft and driven shaft being universally movable in relation to each other from a position wherein the central axes thereof are in alignment with each other and the central axes extending parallel to the handlebar when in alignment, (g) a transmission connecting the pedal unit to the rear wheel for transmitting a drive thereto, (h) a transmission connecting the rear wheel to the driving shaft for transmitting the drive of the rear wheel to the driving shaft whereby a drive is imparted to the driving shaft, and (i) a transmission connecting the driven shaft to the front wheel for transmitting the drive of the driving and driven shafts to the front wheel.
 2. The bicycle of claim 1, wherein the handlebar is rotatable about a swivel axis and the driving shaft and driven shaft extend at respective sides of the swivel axis, the aligned central axes thereof extending perpendicularly to the swivel axis and the swivel axis intersecting the central axes at a common point of intersection.
 3. The bicycle of claim 1, further comprising a bearing element affixed to the handle bar, the driven shaft being rotatably mounted in the bearing element, and another bearing element affixed to the frame, the driving shaft being rotatably mounted in the other bearing element.
 4. The bicycle of claim 1 wherein the transmissions connecting the rear wheel to the driving shaft and the driven shaft to the front wheel comprise roller chains, further comprising sprockets engaged by the roller chains and respectively affixed to the driving and driven shafts for rotation therewith.
 5. The bicycle of claim 4, further comprising additional sprockets respectively affixed to the front and rear wheels, the additional sprockets being engaged by the roller chains.
 6. The bicycle of claim 5, wherein the rear wheel comprises a hub and the additional sprocket affixed to the rear wheel being affixed to the rear wheel hub for rotation therewith.
 7. The bicycle of claim 6, further comprising a detachable coupling arrangement affixing the additional sprocket to the rear wheel hub.
 8. The bicycle of claim 6, wherein the front wheel comprises a hub, further comprising a freewheeling arrangement affixing each of the additional sprockets respectively to the front and rear wheel.
 9. The bicycle of claim 1, further comprising a casing covering the transmission connecting the driving shaft to the rear wheel.
 10. The bicycle of claim 9, wherein the casing includes a guide element for the transmission, the guide element consisting of an abrasion-resistant material having a low friction coefficient.
 11. The bicycle of claim 9, further comprising attachment means for affixing the casing to the frame.
 12. The bicycle of claim 1, wherein the transmissions respectively connecting the front and rear wheels to the driven and driving shafts extend in parallel planes spaced a small distance apart from each other. 